1. Field of the Invention
The present invention pertains to an apparatus designed to drive the tool of a jack hammer drill in rotation.
2. Description of the Prior Art
In the prior art jack hammers the above mentioned rotation of the tool is induced by an apparatus which includes a free sprocket wheel, which is designed to receive ratchets that are supported by radial springs. This traditional apparatus has several disadvantages.
Two ratchets are generally used, which are spaced half a pitch from one another (the pitch referred to, being that of the sprocket wheel). The fragility of the apparatus is therefore due to the fact that only one ratchet is meshed at any given time to induce the rotation of the tool.
The ratchet return springs are continuously subjected to tension and compression forces, everytime a gear of the sprocket wheel meshes. The springs easily lose their elasticity.
The mounting of the free sprocket wheel, on the piston, requires special provisions for the positioning of the ratchets and springs. Thus, the traditional tool rotating apparatus used on jack hammers requires a considerable increase of the working diameter of the jack hammer body.
The installation and assembly of the drill is time consuming and the drill is difficult to operate.
The aforementioned disadvantages should be eliminated by the present invention which calls for a rotating apparatus that is directly controlled by a reciprocating piston, through an axial shift dog.